Yeah, but you can have mechanical cash registers that aren't electronic. And the Wizarding World doesn't use telephones.

I'm talking about the Muggle stores next to the Leaky Cauldron, because it's actually in the Muggle world, not the Wizarding world. The Muggles have never noticed the Leaky Cauldron but surely they would have thought something was odd if electronics didn't work in the area. Sorry that this is sort of going off on a tangent from the original question, by the way.